This post illustrates how you can accomplish adding sections to the left pane, and moving the pages pane from the right-hand side to the left as seen above.
Move Sections from Top to Left
In a recent training session, I was asked if it were possible to move sections from the top to the left in OneNote. The answer is “sort of”. We can get sections on the left also, but we can’t get rid of them from the top. There are two ways to accomplish this: